Dry lubricant coating of extruded tubing

ABSTRACT

A dry lubricant is applied to the interior surface of an extruded tubing to assist in the placement of the tubing on piping. As the tubing is emerging from the extruder, mica powder is sprayed on the inside of the tubing. The mica powder is placed on the inside of the tubing by a rotating feed structure which forces the powder into the interior of the tube. A vibrating hopper is used to hold the mica powder in a nonpacked state. The apparatus is particularly useful with an in-line extruding head.

United States Patent Bagley et al.

[ 51 July 25,1972

[54] DRY LUBRICANT COATING OF EXTRUDED TUBING [72] Inventors: Donald H. Bagley, East Freetown; Richard L. Erickson, Braintree, both of Mass.

[73] Assignee: Armstrong Cork Company, Lancaster, Pa.

[22] Filed: June 18, 1970 [21] Appl. No.: 47,360

52 us. Cl ..425/95, 425/380, 425/131,

425/200 51 Int. Cl ..B29d 23/04 58 FieldofSearch ..18/l4H, 12 SH; 222/198 [56] References Cited UNITED STATES PATENTS 2,199,425 5/1940 Waring ..18/l4 H X 2,576,444 11/1951 Clinefelter ..l8/l4 H X 2,905,365 9/1959 Thayer et al ..222/198 3,183,288 5/1965 Taylor et al. 1 8/14 H X 3,285,200 11/1966 Slaybaugh et al. ..18/12 SH UX Primary Examiner.l. Spencer Overholser Assistant Examiner-Michael 0. Sutton Attorney-Clifford B. Price [57] ABSTRACT A dry lubricant is applied to the interior surface of an extruded tubing to assist in the placement of the tubing on piping. As the tubing is emerging from the extruder, mica powder is sprayed on the inside of the tubing. The mica powder is placed on the inside of the tubing by a rotating feed structure which forces the powder into the interior of the tube. A vibrating hopper is used to hold the mica powder in a nonpacked state. The apparatus is particularly useful with an in-line extruding head.

1 Claim, 1 Drawing Figure DRY LUBRICANT COATING OF EXTRUDED TUBING CROSS-REFERENCE TO COPENDING APPLICATION The invention herein is a modification of the apparatus set forth in Application Ser. No. 793,488, filed .Ian. 23, 1969, in the name of Earl E. Heinzelman, now US. Pat. No. 3,579,732, issued May 25, 1971.

BACKGROUND OF THE INVENTION 1 Field of the Invention The invention relates to an apparatus for lubricating the interior surface of an extruded tubing as it leaves the extruder.

2. Description of the Prior Art In apparatus for extruding from rubber or plastic continuous lengths of tubular or closed cross-sectional material such as hoses, inner tubes, sealing gaskets, etc., it is usually necessary to insert a lubricant of some type into the interior of the extrusion to coat the surface so as to prevent the sticking together of the walls if they collapse. Also, with a tubing which is meant to slide over piping, it is desirable to have a lubricant on the internal surface of the tubing to assist in the sliding of the tubing over the piping. Also during the extruding, a void is formed in the center of the tubing; and unless this void is filled with air, the external atmospheric pressure will tend to collapse the tubing and possibly cause sticking of the sidewalls to form a permanent bond therebetween and, therefore, a flattencd tube.

Soap stone, mica dust, zinc stearate and other dry dust lubricants have been used extensively in the prior art to eliminate the above problems. Also, many different apparatuses are available for applying the dry powders to the interior of the tubing. When mica dust is used, it is very important that the dust be kept as a powder because of the tendency of mica to pack itself into lump-like structures. The spraying of the mica powder on the interior walls will provide a good coating to the interior walls of the tubing. The pushing of lumps of mica into the interior of a piece of tubing will not provide a good coating to these interior walls; and, therefore, collapsed sidewall structures could tend to stick together and maintain the tube in a collapsed state. Also, good lubrication is only secured when a mica powder completely coats the interior wall of the tubing. Therefore, the object of the apparatus herein is to provide a mica dusting apparatus which provides a complete uniform coating to the interior wall of the tubing. The apparatus herein is for use with an in-line extruding head and differs substantially from that of the above-mentioned copending application which is directed to a cross-head extruder.

SUMMARY OF THE INVENTION The invention herein is directed to a mica dispensing apparatus for applying mica dust to the interior walls of an extruded tubing. A rotating drive structure forces the mica dust out to the core pin of the extruder so that the mica dust is sprayed onto the interior walls of the newly extruded tubing. The tendency of the mica dust to pack itself into lumps is eliminated by vibrating the hopper which contains the mica dust. Also, the spring-like structure of the rotating drive structure breaks up any lumps that may exist in the mica powder. The mica dispensing apparatus is so positioned relative to an in-line extruder so that it does not interfere with the operation of the extruder in forming the extruded tube.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a cross-sectional view of the extruder and lubricant feeding structure.

DESCRIPTION OF THE PREFERRED EMBODIMENT screw structure 4 which forces the extrudate through the passageway 5 toward the extruding head 3. The extruding head 3 has the conventional core structure 6 which is utilized to form the internal diameter of the extruded tube. The extrudate passes around the core pin 6 and out the opening 7 of the extruding head die. The core pin 6 forms the internal diameter of the extruded tubing while the outer diameter of the opening 7 forms the outer dimension of the extruded tubing. This apparatus is called an in-line extruding head structure because the core pin and extruder head die are directly in line with the feed of the extruder body 2 and feed screw 4.

It is desirable that the internal diameter of the tubing 8 be coated with a substance which would prevent the internal walls from sticking together if the tubing should be squeezed together. Also, it is desirable that the internal walls of the tubing be provided with a lubricant so that the tubing may be slid readily over a pipe structure. Mica powder is an excellent lubricant and antistick agent for use on the internal walls of the tubing. For the mica powder to be of any value to prevent sticking, it must be applied to the internal walls of the tubing as soon as it leaves the extruding die. The placing of the mica powder on the internal walls of the tubing is accomplished by use of the dispensing mechanism 9 which has a mica feed structure 10 passing through the hollow core pin 6.

The feed structure 10 is composed of a spring-like member 11 which is driven by a motor means 12 in a rotating manner. This spring means passes through a hopper 13 which contains the mica 14. A vibrating apparatus 15 vibrates the hopper to keep the mica in an agitated state so that it will not form lumps. The spring-like member 11 passes through the hopper of mica and picks up the mica and forces it down through a housing 16. The housing 16 is connected to the extruder body 2 and passes from the extruder body 2 to the core pin 6 through one of the support elements 17 which supports the core pin in position in the passageway of the extruder head die 3. The feed screw 11 turns within the core pin and passes through a bore of the core pin until it emerges at the opening 18 of the core pin. The rotating action of the spring-like element ll forces the mica from the hopper down through the extruder body and core pin and out the opening 18 where it is dusted against the inside wall of the extruded tubing 8.

What is claimed is:

1. In an extruder structure for forming hollow tubular devices, a core pin used to form the internal diameter of the tube while the extruder head die forms the external diameter of the tube, the core pin being placed within an opening in the head die, means in line with the core pin and die feeding extrudate directly to the core die and forcing the extrudate through the core die and around the core pin to form the hollow tubular device, the improvement comprising a passageway in the center of the core pin with an opening where an extruded tube emerges from the extruder head die, a curved passageway in the extruder structure connected with the passageway in the core pin, a vibrating hopper containing dry powder lubricant, and helical spring-like rotating means passing through the hopper of dry powder lubricant and through the passageways of the extruder structure and core pin to force dry lubricant from the vibrating hopper through the passageways and out the opening in the core pin to dust dry lubricating powder on the internal walls of an extruded tube. 

1. In an extruder structure for forming hollow tubular devices, a core pin used to form the internal diameter of the tube while the extruder head die forms the external diameter of the tube, the core pin being placed within an opening in the head die, means in line with the core pin and die feeding extrudate directly to the core die and forcing the extrudate through the core die and around the core pin to form the hollow tubular device, the improvement comprising a passageway in the center of the core pin with an opening where an extruded tube emerges from the extruder head die, a curved passageway in the Extruder structure connected with the passageway in the core pin, a vibrating hopper containing dry powder lubricant, and helical spring-like rotating means passing through the hopper of dry powder lubricant and through the passageways of the extruder structure and core pin to force dry lubricant from the vibrating hopper through the passageways and out the opening in the core pin to dust dry lubricating powder on the internal walls of an extruded tube. 